Generally, corporate information systems have shared storage, where multiple physical servers access a single storage device and share data in the storage device. Use of such a configuration allows data to be controlled centrally, as well as allows the hot-standby function, the backup function, or the like for enhancing the availability of the servers to be used effectively. In a server virtualization environment, the migration function which is an ability to migrate a virtual server from currently running physical server to another physical server, requires shared storage. Because it is needed to refer data each other. Because it need to refer the same data between the source and destination physical servers to execute migration. Shared storage is constructed using the NAS (Network Attached Storage) technology, in which a file is shared between different servers, or the SAN (Storage Area Network) technology, in which block storage is shared using a protocol such as FC (Fibre Channel) or iSCSI (Internet Small Computer System Interface).
On the other hand, there are corporate information systems which do not need shared storage. Examples of such systems include distributed processing systems of big data, typified by Hadoop, and Web server load balancing systems using a load balancer. In these systems, different servers do not need to share data. Therefore servers often use the local disks to store data rather than using shared storage.
Currently, both these two types of corporate information systems, which are different in data storage place, exist in the same environment. Which of the local disk and shared storage should be used as a data storage place is determined depending on the requirements for the corporate information system. Since a local disk is generally cheaper than shared storage, corporations seeking to reduce cost desire to use local disks.